A well-known optical fiber communications network is the passive optical network. Such networks typically use time division multiplexing from a central terminal controller to several remote customer terminals and time division multiple access from the customer terminals to the central terminal controller over one or two fibers. Known systems were designed to support circuit-based services including telephony, low speed data, and residential video. Passive optical networks have been used in limited deployments mainly due to the relatively high cost of components, system complexity and high price points for residential customer services.
Emerging broadband service providers seek to build network infrastructure to deliver multiple broadband services to business customers. Whereas traditional networks have been circuit-based, new network infrastructures are largely based on Internet Protocol (IP) packet-based or Asynchronous Transfer Mode (ATM) cell-based technologies. The ITU-T Recommendation G.983.1 xe2x80x9cBroadband Optical Access System Based On Passive Optical Networks (PON)xe2x80x9d discloses ATM cell-based PONs.
There is a need for a way to provide both packet-based and cell-based broadband services over a low cost, high bandwidth access network.
The present method and system provide an approach to support the aggregation of multiple broadband services including voice, high speed data, video and image through the transmission of packets and cells simultaneously over a PON.
Accordingly, a method of communication between a central terminal and plural remote terminals over a passive optical network having a downstream portion and an upstream portion includes transmitting downstream data from the central terminal to the plural remote terminals in successive downstream frames over the downstream network portion and transmitting upstream data from the plural remote terminals to the central terminal in respective upstream timeslots over the upstream network portion, the upstream timeslots forming successive upstream frames. The downstream data includes downstream packet data and downstream ATM cell data and the upstream data includes upstream packet data and upstream ATM cell data. The upstream data can be transmitted from at least one of the plural remote terminals in multiple upstream timeslots which can be non-contiguous.
According to the present approach, a communication system includes a shared medium, e.g., a passive optical network, having a downstream portion and an upstream portion, a central terminal and a plurality of remote terminals coupled to the shared medium for communicating with the central terminal. The central terminal transmits downstream data to the plural remote terminals in successive downstream frames over the downstream shared medium portion, the downstream data including downstream packet data and ATM cell data. The plural remote terminals transmit upstream data to the central terminal in respective upstream timeslots over the upstream shared medium portion, the upstream timeslots forming successive upstream TDMA frames, the upstream data including upstream packet data and ATM cell data.
Each downstream frame comprises a first number of downstream subframes each of which includes a second number of downstream timeslots. Each downstream timeslot has one of a plurality of downstream formats which include a downstream packet format for carrying downstream packet data and a downstream cell format for carrying downstream ATM cell data. The downstream subframe further includes a downstream communication channel for communicating downstream control information (e.g., provisioning information) to the remote terminals.
The downstream packet format for carrying downstream packet data includes a downstream packet header and a downstream packet payload for carrying a portion or all of a single downstream packet. The downstream packet header includes a first field identifying at least one of the plural remote terminals to receive the downstream packet data, a second field identifying a port of the at least one remote terminal identified in the first field to terminate the downstream packet data and a third field indicating whether the corresponding downstream packet payload includes an end of packet.
The downstream cell format for carrying downstream ATM cell data includes a downstream cell header and a downstream cell payload. The downstream cell header includes a first field identifying at least one of the remote terminals to receive the downstream ATM cell data. The downstream cell payload includes an ATM cell header having a first field identifying a port of the at least one remote terminal identified in the downstream cell header to terminate the downstream ATM cell data.
Each upstream timeslot includes an upstream header and an upstream payload. The upstream header includes a first field for a guard time, a second field comprising an upstream timeslot sync pattern for synchronizing phase alignment of the upstream data received at the central terminal, a third field comprising an upstream timeslot start delimiter for byte alignment of the upstream data received at the central terminal and a fourth field comprising an upstream communication channel for communicating upstream control information to the central terminal from the respective remote terminal.
Each upstream timeslot has one of a plurality of upstream formats which include an upstream packet format for carrying upstream packet data and an upstream cell format for carrying upstream ATM cell data.
The upstream packet format for carrying upstream packet data includes an upstream packet header and an upstream packet payload; the upstream packet header including a first field identifying a next packet start byte in the upstream packet payload and a second field indicating length of the upstream packet payload. The upstream packet payload includes at least a portion of a packet and can include multiple packets.
The upstream cell format for carrying upstream ATM cell data includes an upstream cell header and an upstream cell payload; the upstream cell header including a first field identifying a next ATM cell start byte in the upstream cell payload and a second field indicating length of the upstream cell payload. The upstream cell payload includes at least a portion of an ATM cell and can include multiple ATM cells.